اثر منابع مختلف نیتروژن و کودهای آلی بر عملکرد و اجزای عملکرد گیاه دارویی زنیان (Trachyspermum ammi L.)

Introduction
Ajowan (Trachyspermum ammi L.) is an annual medicinal plant of the family Apiaceae which can reach 30 -100 cm in height. and its growth is highly depended on the availability of mineral nutrients in the soil. But, it has been shown that utilization of chemical fertilizers for growth promotion of Ajown could have negative impacts on environment and ecological systems. Nowadays, sustainable agriculture is the best approach to overcome such problems and prevent the excess accumulation of chemical fertilizers deposited within the soil. Application of bio-fertilizers as an alternative to chemical fertilizers is a new sustainable approach which have been raised in the new era of Agriculture. Therefore, this study was conducted to investigate the application of various source of biological fertilizers such as Vermicompost, Alkazotplus and Humic Acid in combination with nitrogen fertilizers on growth behavior, yield and yield components of Ajowan under Ahvaz growing condition.
Materials and methods
This research was conducted at the Agricultural Research Station of Shahid Chamran University in 2014-2015 to determine the effects of different sources of nitrogen and organic fertilizers on the yield and yield components of Ajowan based on two way randomized complete block design with three replications. The first factor of the experiment was Application of four different nitrogen sources including: Urea (U), Sulfur-coated Urea (SCU), %50 Sulfur-coated urea (1/2 SCU) + Alkazot Plus biological fertilizer and Control (no nitrogen source used). Organic fertilizers were also applied at four levels, consisting of Humic Acid, Vermicompost, %50 Vermicompost + Humic Acid and Control (no organic Fertilizer) as the second factor. After soil preparation, approximately four Kg.ha-1 of the seeds were planted on the rows with 30 cm distance. Plant height, number of sub branches, number of umbels per plant, number of seeds per umbel , 1000 seeds weight, biological and grain yield and harvest index were measured during vegetative and maturity stage of plant growth.
Results and Discussion
The results of the experiment showed that the interaction between different sources of nitrogen and organic fertilizers on plant height, number of umbrella per plant, number of seeds per umbrella, biomass and grain yield were significant. Also most of plant growth characteristics under either no nitrogen or no organic fertilizers were gained the lowest values. On the other hand, it seems that combination of chemical and biological fertilizers can improve plant trait performances in Ajowan. The highest plant height (117.8 cm) was measured in the treatments received slow release Urea combined with Vermicompost. The highest seed per umbel (424.3) was observed at the %50 rate of Vermicompost + Humic Acid and without nitrogen fertilizer (control) and the biggest amount of 1000 seeds weight (1.14 g) was measured at the %50 rate of slow release urea with Alkazotplus + Humic Acid. Also the highest umbel per plant (82.27), biological yield (8507.1 Kg.ha-1) and grain yield (1670 Kg.ha-1) were obtained at Vermicompost + Urea fertilizer and finally the highest harvest index (32%) was related to the %50 rate of slow release urea with the highest value Alkazotplus + Vermicompost. Vahidipour et al (2013) showed that the maximum Essential oil yield and the highest grain yield of Ajowan was gained in application of 200 kg N.ha-1. The results of the current study indicated that most of plant trait improvements were induced by combanitaion of vermicompost with urea fertilizer. As a result, in order to gain maximum plant yield under an environmental friendly situation, it is strongly suggested to implement Vermicompost in combination with minimized application of urea fertilizer. This could be an important economic and sustainable approach.
Conclusion
Totally the results of this research showed that the application of Vermicompost purely and in combination with urea, had a significant effect on the yield and growth characteristics of Ajowan. Findings of this research also revealed that organic fertilizers like Vermicompost especially its integrated application with chemical fertilizers and proper agronomical management had significant effect on the Ajowan yield. In order to increase the production of medicinal plants in low input agricultural systems and due to positive effects of organic fertilizers on soil sustainability, long term production process, prevention of environmental pollution and finally supplying proper and qualitative food, this fertilizer purely and with combination of minimized rates of chemical fertilizer could be important in reaching to sustainable agriculture goals and decreasing application of chemical fertilizers.